This application claims the benefit of Japanese Application No. 2001-096843 filed in Japan on Mar. 29, 2001, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a lens barrel in which an optical axis can be adjusted and to a method of assembling the same.
2. Description of the Related Art
Conventionally, various proposals have been made for an optical axis adjustment mechanism of lens groups in a lens barrel used in cameras, and the like. For example, Japanese Unexamined Patent Application Publication No. 11-305106 discloses an optical axis adjustment mechanism used in a lens barrel employing an optical system, and the optical axis adjustment mechanism advances and retracts lens groups for focusing and zooming.
In this conventional optical system lens barrel, three helicoid pieces are attached to a lens group frame by screws to support the lens group frame such that it is free to advance and retract with respect to a main lens barrel member. Adjustment spacers are inserted into the helicoid pieces to prevent the backlash between helicoid thread on the lens barrel main body side and the helicoid pieces and simultaneously to adjust the center axis of the optical axis of the lens groups.
However, assembly is time-consuming in the arrangement disclosed in Japanese Unexamined Patent Application Publication No. 11-305106 because it requires inserting the adjustment spacers in each lens group frame. Further, the optical axis can be adjusted only in a direction perpendicular to the optical axis, and the inclination of the optical axis cannot be adjusted.
Further, there is also a method of providing a gap at the portion where the lens group frame is supported and bonding and securing lens groups such that they are centered from the outside. However, workability is not good in this bonding method because variation with time must be taken into consideration and further bonding is required.
Furthermore, as a generally employed optical axis adjustment method, there is also a method of obtaining a desired accuracy for an optical axis by correcting a metal mold while measuring the decentering of an optical axis positioning member acting as a molded member. In this method, however, it is necessary to perform adjustment again when the molding conditions change, thus requiring a long preparation time to produce parts.
An object of the present invention, which was made to overcome the above disadvantages, is to provide a lens barrel in which the position of the optical axis of the lens barrel and/or the inclination of the optical axis thereof can be easily adjusted, and to provide a method of assembling the lens barrel.
The lens barrel of the present invention includes a first frame member for supporting lenses; a second frame member for holding the first frame member; and a plurality of adjustment members interchangeably secured to the first frame member, each of the plurality of adjustment members including an abutment portion, which abuts on the second frame member in an optical axis direction to adjust the amount of inclination of the lenses with respect to the optical axis of other lenses in the lens barrel through the second frame member, and an inserted portion that is inserted between the first frame member and the second frame member to adjust the decentering between the optical axis of the lenses and an optical axis of other lenses in the lens barrel through the second frame member. With this arrangement, the amount of inclination and the amount of decentering of the lenses with respect to the optical axis of the other lenses are adjusted by selectively changing the adjustment members that are abutted on the second frame member to determine the relative position thereof and fixing the adjustment members to the first frame member.
Further, in a method of assembling a lens barrel of the present invention that includes a first frame member for supporting lenses, a second frame member for holding the first frame member, and a plurality of adjustment members detachably secured to the first frame member, each of the plurality of adjustment members including an inserted portion inserted between the first frame member and the second frame member to adjust the decentering between the optical axis of the lenses and an optical axis of other lenses in the lens barrel through the second frame member as well as including an abutment portion abutting on the second frame member in an optical axis direction to adjust the inclination between the optical axis of the other lenses in the lens barrel and an optical axis of the lenses through the second frame member, the method includes the steps of assembling a plurality of adjustment members, each of the plurality of adjustment members having the same shape, on the lens barrel; measuring the amount of decentering and the amount of inclination of the lenses; selecting adjustment members from a plurality of kinds of adjustment members each having a combination an inserted portion produced in a different size and an abutment portion produced in a different size based on the measured amount of decentering and inclination of the lenses; and assembling the selected adjustment members on the lens barrel.
Other featuers and advantages of the present invention will become more apparent from the following description.